After activation, T-cells express a set of genes which encode the inducer cell's functional program. Other T-cell genes define the essentials of the cell's specialized physiology in terms of normal and neoplastic growth. To identify these genes, we have screened a panel of cDNAs which are selectively expressed by resting and activated T-cell clones. The transcription of one such gene, TCR- 7, decreases after activation. The deduced sequence of the TCR- 7 predicts a 41,330 dalton intracellular protein. The TCR-7 gene encoding this protein maps by RFLP near the HBB locus on chromosome 7. Further analysis of TCR-7 expression suggests the possibility that it may negatively regulate IL-2 receptor expression in L3T4+ inducer cells but not Ly2+ T-cells. We have also developed a panel of T-cell clones that co-recognize hapten and MHC products. Although there is good evidence that genes encoding alpha and beta heterodimers account in some fashion for co-recognition by T-cells, the structural basis for recognition of antigen-MHC complexes is not clear. The protocols and methodology detailed in Specific Aim II are intended to directly establish the structural contribution of the alpha and beta chains to T-cell recognition of antigen, using clones that are specific for well-defined haptens.